The count parameter is the number of elements in the array you're modifying, or 1 if you're not modifying an array. The number in the function name is the size of an element. 1 means scalar (float, int, uint, etc). 2 means 2-element vector (vec2, ivec2, uvec2, etc). And so on.

If you're modifying a single vec2, you use glUniform2fv(..., 1, <array of two floats>);. If you're modifying a `vec2[3]`, then you use glUniform2fv(..., 3, <array of 2 * 3 floats>);